The present invention relates to vapor control valves for vehicle fuel tanks, and particularly to multi-stage vapor control valves. More particularly, the present invention relates to a tank-mounted valve that operates to vent pressurized fuel vapor from a vehicle fuel tank to a vapor recovery canister on board the vehicle.
Vapor control valves are used in fuel tanks to vent fuel vapors generated during refueling due to agitation of the dispensing fuel. In addition, the fuel vapors already present in the fuel tank are displaced by liquid fuel being dispensed into the fuel tank. As the pressure inside the tank increases, that pressure needs to be released. In vehicle tanks without vapor control valves, the pressurized vapor escapes into the atmosphere through a filler neck in the fuel tank. Vapor control valves act to exhaust these displaced vapors to a vapor recovery canister or other such destination outside the fuel tank.
According to the present invention, a vapor control valve assembly is mounted to a fuel tank and includes a housing with a vent inlet and a bypass inlet, both in communication with pressurized vapor in the fuel tank. The assembly further includes a discharge outlet which carries fuel vapor to a vapor-recovery canister and a vent passageway connecting the vent inlet to the discharge outlet. A bypass passageway connects the bypass inlet with a bypass outlet which is in communication with pressurized vapor in the vent passageway. A first closure means positioned in the vent inlet is moveable between opened and closed positions for closing in response to liquid fuel rising in the vent housing. A second closure means is positioned in the bypass outlet and is normally closed. However, the second closure means opens when pressure in the bypass passageway is greater than a predetermined pressure and when the first closure means is in its opened position.
In preferred embodiments, the valve assembly includes a housing mounted in an aperture formed in the top wall of the fuel tank and two valves for controlling the flow of pressurized fuel vapor through the housing from a vehicle fuel tank to a vapor-recovery canister onboard the vehicle. A vent passageway conducts fuel vapor from a vent inlet through the housing to a discharge outlet coupled to the canister and a two-stage vent valve (the first valve) in the tank regulates fuel vapor flow from the tank into the vent passageway.
A bypass passageway conducts fuel vapor from a bypass inlet through the housing to a bypass outlet coupled to the vent passageway and a bypass valve (the second valve) in the housing regulates fuel vapor flow into the vent passageway from the bypass passageway and the tank. The fuel vapor discharged from the bypass passageway through the bypass outlet mixes with fuel vapor passing through the vent passageway and the mixture is discharged from the housing to the canister through the discharge outlet.
The bypass valve is configured to open when the two-stage vent valve is partly opened and a small volume of fuel vapor is venting from the tank to the canister through the vent passageway in the housing. The bypass passageway is sized so that a greater volume of fuel vapor can pass therethrough and be vented to the canister through the discharge outlet even though only a small volume of fuel vapor is being allowed to vent by the two-stage vent valve in response to certain pressure conditions in the tank.